A Wednesday 18 October raid by Pinellas County Sheriff's Office on a home linked to a child porn investigation uncovered a hidden arsenal of weapons and a note that said "the world will burn", authorities said.

24-year-old Randall Drake, who lived at the Florida home with his parents, was arrested and charged with two counts of unlawfully making, possessing, or attempting to make a destructive device.

Authorities said that inside a locked closet they found weapons including an AK-47 assault rifle, a 50-caliber pistol, 2,300 rounds of ammunition and a baseball bat with nails protruding from it. There were also explosives and a homemade silencer.

Pinellas County Sheriff Bob Gualtieri told reporters in a press conference on Thursday 19 October that investigators also found aerial images of two schools and a local water treatment plant. The note they discovered read: "My fury at those who imprisoned me shall be vast and without mercy. I shall have my bloody revenge, and then the world will burn".

"I don't know what his plan was," Gaultieri said, according to the Associated Press. "He had all kinds of books and all kinds of gun powder and if he had taken those devices put them in something else and put a bunch of nails and screws and other things, he could have caused some serious damage. Because it's the shrapnel that hurts and kills everybody."

Drake did not have a criminal history. Authorities said he had previously lost a job at Florida Firearm Academy after arriving to work with guns strapped to his thighs.

"These are the people who are most concerning to us," Gaultieri said, comparing Drake to Stephen Paddock, the man who shot 58 people dead in Las Vegas. "What we call the lone wolves, the sleepers who are out there, the people who are not on our radar, the people who have fallen under the radar or off of it. You don't know about them until they engage in devastating acts and kill a whole bunch of people."